1. Field of the Invention
The present invention relates to a method and an apparatus for liquid preparation of a photographic reagent, and more specifically, to a liquid preparation method for a silver halide emulsion for use in a heat-developable photosensitive material.
2. Description of the Related Art
The photosensitive material is classified broadly into the silver halide photographic sensitive material which uses a gelatin-based binder and the heat-developable photosensitive material which uses a polymer latex-based binder such as an SBR (styrene-butadiene copolymer)-based binder, either photosensitive material using a silver halide emulsion.
A heat-developable photosensitive material which contains an organic silver salt, a reducing agent for silver ion, a polymer latex, and a photosensitive silver halide emulsion, and the like is used as a coating liquid for use in image formation. In this case, the coating liquid is prepared by adding a small amount of the silver halide emulsion to a mother coating liquid containing the organic silver salt, the reducing agent for silver ion, the polymer latex, and the like.
On the other hand, as for the silver halide photographic material, a large amount of the silver halide emulsion is consumed, and accordingly the liquid preparation of the silver halide emulsion has been made with the so-called system line for continuous liquid preparation, as disclosed in Japanese Patent Application Publication No. 47-30315, in which the silver halide emulsion is continuously melted in a heating tank heated by a heating device and a required amount is continuously taken out and measured.
Generally, the liquid preparation operations in the production of the silver halide emulsion include a process for preparing silver halide grains and a process of adding a sensitizing dye. The preparation of silver halide grains is made by a liquid preparation method in which a solution of a water soluble silver salt and a solution of a water soluble halide are mixed together and allowed to react with each other, and there have been used such mixing reactors for reaction by mixing as described in Japanese Patent Application Publication No. 51-83097, U.S. Pat. No. 3,785,777, Japanese Patent Application Publication No. 60-117834, Japanese Patent Application Publication No. 57-92524, and Japanese Patent Application Publication No. 48-21045. The addition of the sensitizing dye is made subsequently to the preparation of silver halide grains.
In the case of the heat-developable photosensitive material, however, the used amount of the silver halide emulsion is extremely smaller as compared with the silver halide photographic material, and hence there is a drawback that the quality deterioration occurs in the prepared liquid remaining in the heating tank with elapse of the time (hereafter referred to as xe2x80x9ctime elapse in meltxe2x80x9d) when the conventional liquid preparation method is applied in which the silver halide emulsion is melted continuously in the heating tank heated by the heating device and the amount required for liquid preparation is continuously measured and taken out from the tank. When the used amount is small, there is a problem that the quality deterioration and the reagent loss are enhanced due to the residuals in the conduit pipe in the system line for continuous liquid preparation. Furthermore, the sensitizing dye used in the heat-developable photosensitive material is required to avoid mutual contamination of different kinds of dyes, but it is the case in a conventional liquid preparation apparatus that no equipment is arranged for preventing the mutual contamination. As for the problems of the time elapse in melt, reagent loss and mutual contamination, they are not restricted to the liquid preparation of the silver halide emulsion, but similar troubles occur when the liquid preparation involves a photographic reagent small in its amount used.
On the other hand, as for the silver halide grains in the production of the silver halide emulsion, the diameters of silver halide grains are preferably to be made small, and particularly, in the case of the silver halide emulsion for use in the heat-developable photosensitive material, it is essential to make the grain diameter small and to make the distribution width of the grain diameter narrow for the purpose of suppressing the white turbidity occurring after image formation. In this connection, however, there is a problem that neither satisfactory grain diameters nor a satisfactory distribution width of grain diameter can be obtained by simply using the above-described conventional mixing reactor as it is.
In the process for producing the silver halide emulsion, not only a single kind of emulsion is produced but also different emulsions added with other kinds of sensitizing dyes are produced, and accordingly the contamination of the sensitizing dye occurs if the sensitizing dye used in the last production operation is insufficiently removed at the time of lot renewal, leading to a production failure. In particular, when the sensitizing dye used in the production of the silver halide emulsion for use in the heat-developable photosensitive material contaminates other emulsions, such serious production failures as adverse generation of fog and the like are caused, and hence sufficient removal of the dye is required. Conventionally, the removal of the sensitizing dye remaining in the apparatus in the process is made by warm-water rinsing, acid-solution rinsing, alkali-solution rinsing, and combinations thereof, where there is a problem of persisting silver grains when some portions of the physical objects to be rinsed get away from the rinsing liquids. In addition, there is also a problem that a dedicated equipment is required for disposing the rinsing liquid wastes and the running cost is increased.
The present invention has been made in view of these above-mentioned circumstances, and an object of the present invention is to provide a method and an apparatus for liquid preparation of photographic reagents which can effectively prevent the problems of the time elapse in melt, and the loss and mutual contamination of reagents, in the liquid preparation of photographic reagents. Another object of the present invention is to provide a method and an apparatus for production of a silver halide emulsion which can reduce the grain diameter and distribution width thereof in the production of silver halide grains for use in the production of a silver halide emulsion, and can also simply deactivate the sensitizing dye remaining in the process of adding a sensitizing dye without generating rinsing water waste.
In order to achieve the above-mentioned objects, the present invention is directed to a method for liquid preparation of photographic reagent comprising at least a process of measuring the photographic reagent and a process of heat-melting the photographic reagent, the method comprising the steps of: transferring, with a pump, the photographic reagent to be measured to a measuring tank via piping without being heated; heating the photographic reagent to be melted after measuring; and repeating the steps for every liquid preparation.
In addition, in order to achieve the objects, the present invention is also directed to an apparatus for liquid preparation of photographic reagent comprising at least a device for measuring the photographic reagent and a unit for heat-melting the photographic reagent, the apparatus comprising: a container for storing the photographic reagent; a measuring tank equipped with a heating device; and a transfer pump rotatable both forward and backward which transfers the photographic reagent in the container to the measuring tank via piping.
According to the present invention, for every liquid preparation a series of the processes are repeated wherein photographic reagents are transferred by a pump via a piping without being heated to a measuring tank, measured, and undergo heat-melt after being measured. Thus, it is possible to make the time of heating the photographic reagent as short as possible, in the whole time course of the liquid preparation of the photographic reagent, and hence the time elapse in melt can be suppressed. Since a series of processes of liquid transfer, measuring, and heat-melt are repeated for every liquid preparation, that is, this is a batch-wise method, it becomes easy to deal with the loss and mutual contamination of reagents. In other words, by letting the pump to rotate backward and blowing the air into the conduit pipe from the transfer-directional end of the piping, the photographic reagent remaining in the piping can be recovered through this backward washing, and hence the loss and mutual contamination of reagents can be suppressed.
The method and apparatus of the present invention are suitable for the method and apparatus for liquid preparation of a silver halide emulsion for use in a heat-developable photosensitive material as a photographic reagent.
In order to achieve the above-mentioned objects, the present invention is also directed to a method for producing a silver halide emulsion in which in a preparation process of preparing silver halide grains by mixing and reacting a solution of a water soluble silver salt with a solution of a water soluble halide for production of a silver halide emulsion, a mixer having an opening for circulation is arranged in a reactor filled with a colloidal aqueous solution, and while the respective two solutions are separately added to the opening for circulation from the respective reacting solution feeding pipes to be diluted in the mixer by the colloidal solution filling thereof, silver halide grains are produced by rapidly mixing by a first stirring device both solutions to be allowed to react with each other, and a circulating flow of the colloidal solution is generated by a second stirring device which flow starts from the mixer to reach the reactor and goes back to the mixer through the opening for circulation; wherein the circulating flux of the circulating flow is made not smaller than 500 L/min. at the opening for circulation under the preparation condition that silver halide grains are prepared by adding the solution of a water soluble silver salt at the rate of not smaller than 4 kg/min. as converted to the weight of silver.
According to the present invention, the solution of a water soluble silver salt and the solution of a water soluble halide are added through the respective reacting-solution feeding pipes, made to flow into the mixer while being diluted at the opening for circulation, mixed and allowed to react with each other in the mixer to produce silver halide grains. In this connection, although it is possible to reduce the silver halide grain diameter and distribution width thereof by reducing the concentrations of the reacting solutions, that is, the solutions of a water soluble silver salt and a water soluble halide, a realistic unit in accord with this manner is impossible in view of the productivity. Thus, it is required that the silver halide grain diameter and distribution width thereof can be made small even with the addition of the solution of a water soluble halide in such an amount, as converted to the weight of silver, that the unit works as a realistic one. Accordingly, in the present invention, under the condition that the preparation of silver halide grains is made by adding the solution of a water soluble silver salt at a rate of 4 kg/min. as converted to the weight of silver, the circulating flow rate of the circulating flow at the opening for circulation is set not to be smaller than 500 L/min. By setting the circulating flow rate of the circulating flow not to be smaller than 500 L/min, both solutions added from the reacting solution feeding pipes can be instantly diluted by the colloidal solution, and hence it is possible to prepare silver halide grains having small diameters with a narrow distribution width thereof, even under the preparation condition that the silver halide grains are prepared by adding the solution of a water soluble silver salt at a rate not smaller than 4 kg/min. as converted to the weight of silver.
As a preferable aspect of the present invention, in addition to the above-mentioned circulating flow rate, it is preferable to complete the reaction in a short time by setting the addition flow rate of both solutions not to be smaller than 20 L/min.
In addition, as another preferable aspect of the present invention, it is recommended to further add the solution of a water soluble silver salt and the solution of a water soluble halide subsequently to preparation of silver halide grains, on the basis of the potential of silver.
In order to achieve one of the above-mentioned objects in the present invention, in the process involving adding sensitizing dyes for production of a silver halide emulsion, after completion of the process the interior of the apparatus in the process is subjected to light exposure wherein the sensitizing dye is deactivated.
In order to achieve the object in the present invention, in the device for adding a sensitizing dye to prepare silver halide grains, a device for light exposure is arranged with which the interior of the apparatus undergoes light exposure.
According to the present invention, the interior of the apparatus is subjected to light exposure after completion of a process to deactivate the sensitizing dye, and hence it is possible to clean infallibly all over the interior mirror surface of the tank. In this manner, no rinsing water waste is generated, and the cost can be reduced.
The method and apparatus for producing silver halide emulsion of the present invention is suitable for the method and apparatus for producing a silver halide emulsion for use in a heat-developable photosensitive material which requires, for the purpose of suppressing the white turbidity occurring after image formation, the smaller diameter of silver halide grains and narrower distribution width thereof than the silver halide grains for use in the silver halide photographic material, and uses a sensitizing dye that causes a serious production failure when it contaminates other emulsions.